1. Field of the Invention
The present invention describes the preparation of high molecular weight copolymeric polyaspartic esters which have been hydrophobically modified with alkyl or alkenyl radicals having from 6 to 30 carbon atoms.
2. Prior Art
Polyamino acid derivatives, in particular polyaspartic acid, have recently attracted particular attention because of their biodegradability and their similarity to naturally occuring structures. Proposed applications are inter alia as biodegradable complexing agents, water softeners and detergent builders. Polyaspartic acid is generally obtained by alkaline hydrolysis of the direct synthesis precursor polysuccinimide (PSI, anhydropolyaspartic acid), the cyclic imide of polyaspartic acid. PSI can be prepared, for example, in accordance with EP 0 578 449 A, WO 92/14753, EP 0 659 875 A or DE 44 20 642 A from aspartic acid, or is obtainable, for example according to DE 36 26 672 A, EP 0 612 784 A, DE 43 00 020 A or U.S. Pat. No. 5,219,952 A, from maleic acid derivatives and ammonia. Proposed applications for these customary polyaspartic acids are inter alia as an encrustation inhibitor, builders in detergents, fertilizer additive and auxiliary in tanning.
The reaction of polysuccinimide with amines, which has been described by various working groups, leads to polraspartic amides (Kovacs et al., J. Med. Chem. 1967, 10, 904-7; Neuse, Angew. Makromol. Chem. 1991, 192, 35-50). The ring opening of polysuccinimide using polyamines and the subsequent alkaline hydrolysis for the preparation of polyaspartic acid derivatives for applications as superabsorbers is described, for example, in WO 95/35337, in WO 96/08523 or in Annu. Tech. Conf. Soc. Plast. Eng. 1995, 53, 1510-13. Neri et al describe, in J. Med. Chem 1973, 16, 893-897 the reaction of polysuccinimide with ethanolamine to give hydroxyethyl polyaspartates for pharmaceutical uses.
For applications inter alia as emulsifier, dispersant and surfactant, copolymeric polyaspartic esters partially esterified with long-chain fatty alcohols or their derivatives are of particular interest. Such compounds are readily obtainable on the basis of maleic monoesters and ammonia, as explained in DE 195 45 678 or EP 96 118 806.7, and generally more usually have low molecular weights.
The object of the invention is to provide copolymeric polyaspartic esters with increased molecular masses.